DENVER (AP) — A federal lawsuit says two gun rights groups worked on political attack mailers in Colorado that showed a gay couple from New Jersey kissing.

The mailers were used in two Colorado Republican primaries last year and cited the issue of civil unions to caution voters against particular candidates who supported legislation providing gay couples protections similar to marriage.

The Southern Poverty Law Center sued on behalf of the gay couple last year and named Virginia-based Public Advocate of the United States as a defendant because their name was on the fliers.

SPLC says in a motion Wednesday they want to add Rocky Mountain Gun Owners and the National Association for Gun Rights as defendants.

A representative from the gun groups did not immediately return a call seeking comment.